The invention relates to reducing hair growth in mammals, particularly for cosmetic purposes.
A main function of mammalian hair is to provide environmental protection. However, that function has largely been lost in humans, in whom hair is kept or removed from various parts of the body essentially for cosmetic reasons. For example, it is generally preferred to have hair on the scalp but not on the face.
Various procedures have been employed to remove unwanted hair, including shaving, electrolysis, depilatory creams or lotions, waxing, plucking, and therapeutic antiandrogens. These conventional procedures generally have drawbacks associated with them. Shaving, for instance, can cause nicks and cuts, and can leave a perception of an increase in the rate of hair regrowth. Shaving also can leave an undesirable stubble. Electrolysis, on the other hand, can keep a treated area free of hair for prolonged periods of time, but can be expensive, painful, and sometimes leaves scarring. Depilatory creams, though very effective, typically are not recommended for frequent use due to their high irritancy potential. Waxing and plucking can cause pain, discomfort, and poor removal of short hair. Finally, antiandrogens—which have been used to treat female hirsutism—can have unwanted side effects.
It has previously been disclosed that the rate and character of hair growth can be altered by applying to the skin inhibitors of certain enzymes. These inhibitors include inhibitors of 5-alpha reductase, ornithine decarboxylase, S-adenosylmethionine decarboxylase, gamma-glutamyl transpeptidase, and transglutaminase. See, for example, Breuer et al., U.S. Pat. No. 4,885,289; Shander, U.S. Pat. No. 4,720,489; Ahluwalia, U.S. Pat. No. 5,095,007; Ahluwalia et al., U.S. Pat. No. 5,096,911; and Shander et al., U.S. Pat. No. 5,132,293.
α-Difluoromethylomithine (DFMO) is an inhibitor of ornithine decarboxylase (ODC). A skin preparation containing DFMO (sold under the name Vaniqa®, has been approved by the Food and Drug Administration (FDA) for the treatment of unwanted facial hair growth in women. Its topical administration in a cream based vehicle has been shown to reduce the rate of facial hair growth in women. Vaniqa® facial cream includes a racemic mixture of the “D-” and “L-” enantiomers of DFMO (i.e., D,L-DFMO) in the monohydrochloride form at a concentration of 13.9% by weight active (15%, as monohydrochloride monohydrate). The recommended treatment regimen for Vaniqa® is twice daily. The cream base vehicle in Vaniqa® is set out in Example 1 of U.S. Pat. No. 5,648,394, which is incorporated herein by reference.
It generally takes about eight weeks of continuous treatment before the hair growth-inhibiting efficacy of Vaniqa® cream becomes apparent. Vaniqa® cream has been shown to decrease hair growth an average of 47%. In one study, clinical successes were observed in 35% of women treated with Vaniqa® cream. These women exhibited marked improvement or complete clearance of their condition as judged by physicians scoring a decrease in visibility of facial hair and a decrease in skin darkening caused by hair. Another 35% of the women tested experienced some improvement in their condition. However, there were some women who exhibited little or no response to treatment.
Accordingly, although Vaniqa® cream is an effective product, it would be even more effective if it provided an earlier onset of hair growth inhibition (i.e., exhibited efficacy earlier than eight weeks) and/or exhibited an increased clinical success rate (i.e., exhibited efficacy in a greater percentage of users).
The stratum corneum serves as a barrier to the influx of pathogens and toxins and the efflux of physiological fluids. The envelopes of the cells in the stratum corneum consists mainly of polar lipids, such as ceramides, sterols and fatty acids while the cytoplasm of the stratum corneum cells remains polar and aqueous. Poor transdermal penetration of some drugs has, until now, frustrated attempts to deliver clinically significant doses by the topical route.
Molecules that are identical to each other in chemical structural formula and yet are not superimposable upon each other are enantiomers. In terms of their physiochemical properties enantiomers differ only in their ability to rotate the plane of plane-polarized light, and this property is frequently used in their designation. Those enantiomers that rotate plane-polarized light to the right are termed dextrorotatory, indicated by either a (+)- or d- or D- before the name of the compound; those that rotate light to the left are termed laevorotatory indicated by a (−)- or l- or L- prefix. A racemic mixture is indicated by either a (±)- or d,l- or D,L- prefix. By another convention (or nomenclature), the R,S or the sequence rule can be used to differentiate enantiomers based on their absolute configuration. Using this system the L-DFMO corresponds to the R-DFMO, and the D-DFMO corresponds to the S-DFMO. Enantiomers are physiochemically similar in that they have similar melting points, boiling points, relative solubility, and chemical reactivity in an achiral environment. A racemate is a composite of equal molar quantities of two enantiomeric species, often referred to as the DL-form. Individual enantiomers of chiral molecules may possess different pharmacological profiles, i.e., differences in pharmacokinetics, toxicity, efficacy, etc.